Aspects of semiconductor technology have focused on enhancing the integration of semiconductor devices (e.g., achieving smaller scale devices). Reducing channel lengths may serve an important role in the development of smaller scale semiconductor devices. Reducing channel lengths may produce undesirable consequences such as a short channel effect.
In order to overcome or otherwise suppress the short channel effect, horizontal reduction and vertical reduction may be employed. Particularly, horizontal reduction in a gate electrode width and vertical reduction in the gate insulating thickness and source/drain junction depth. With horizontal reduction and vertical reduction, an applied voltage is reduced and a doping density of a semiconductor substrate is increased. Particularly, a doping profile of a channel region can be efficiently controlled.
Although reduction in the size of a semiconductor device can be reduced, the necessary power required for operating an electronic device is high. For example, electrons injected from a source in an NMOS transistor may be significantly accelerated in a potential gradient state of a drain, thereby the NMOS transistor may become vulnerable to hot carrier generation. Consequently, a lightly doped drain (LDD) structure may be employed in order to overcome the hot carrier generation.
As illustrated in example FIG. 1, in a transistor having a LDD structure, low-concentration n-type region 104 may be located between channel 102 and high-concentration n+-type source/drain 106. Low-concentration n-type region 104 drops a high drain voltage near a drain junction to prevent a rapid potential gradient, thereby suppressing hot carrier generation.
In order to achieve high integration in semiconductor devices, a variety of technologies for manufacturing a MOSFET having a LDD structure has been suggested. An LDD manufacturing method for forming spacer 105 on sidewalls of gate electrode 103 is one such method. While this method males it possible to obtain a reduction in channel length, its shortcomings is that it produces a reduction in charge mobility. Such reduction in charge mobility causes a reduction in drive current, which in turn, adversely effects the operability of a semiconductor device.